how do you go about getting in the over 50 mph club.

Walter Kaaden, the chief engineer for MZ motorcycles in the 1950s, is generally considered the father of the modern two stroke expansion chamber. He reportedly said "You'll know when you have the design right, because the chamber will then be impossible to fit on the motorcycle without having it drag the ground, burn the rider's leg, or force the relocation of one or more major components."

http://www.dansmc.com/exhaust_2.htm
 
Most 80cc MX bikes rev over 10,000 rpm, compared to our 8000.
What do you do to get the tune right for our operating rpm?


Steve
either do what I did and increase the operating RPM, or do the smart thing and shorten the header pipe
 
The SickBikeParts.com x-chamber works very well.

sunfat66cc7sL-1280.jpg


That thing would do 40+ even with the fat tires and sitting up and no fancy porting or than the normal intake and exhaust.
NGK plug of course, the SBP pipe and 7-speed shifting.
 
Gearing and port timing are important. With any 2 stroke and expansion chamber is always better. Oil ratios also matter but i doubt you could get it past 60mph my Kawasaki Kx100 barely with reed valves barley hits 63. I think with the 66cc with all performance parts you'll top out at maybe a ball hair over 50
 
Wind resistance has a squared relationship to speed. I.e. The resistance at 50 is 4x that at 25. This is where higher hp comes into play. I suggest you look into fabricating some fiberglass fairings and fenders; lower bars etc. I've hit 60 going downhill and man it was downright scary without suspension or anything... Good luck
 
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